There are five sensors, namely; a compass, accelerometer, gyroscope, GPS, and ambient light sensor expected to feature in the new Windows 8 Ultrabooks and convertible tablets. The sensors will give users new ways to interact with their laptops.
(http://zapp5.staticworld.net/images/article/2012/07/five-sensors-available-11390261.jpeg)
image:pcworld
Compass (optional for Ultrabooks): Useful for showing which direction you're facing, so you can automatically get details about landmarks in front of you.
GPS (recommended for Ultrabooks): Pinpoints your location so your device can deliver mapping and other relevant information.
Accelerometer (recommended for Ultrabooks): Detects motion and gravity--often used to protect the hard drive in case a laptop is moved or dropped. Can also give users information (e.g. travel time) based on movement.
Ambient Light Sensor (ALS) (recommended for Ultrabooks): Automatically detects lighting conditions so your laptop can adjust screen brightness based on the surrounding atmosphere.
Gyroscope (optional for Ultrabooks): Similar to the accelerometer--detects rotation and the rate of rotation. Many games make use of this sensor for motion control.
Currently, smartphones and tablets are more capable than laptops when it comes to this smart detection. But the gap may be closing quickly with this next generation of Ultrabooks.
ref:Pcworld